Trogs for the win...uber fast spawn rate, easy to kill and not busy like swoops. Each give around 500 gp, and usually in the first room two are spawning at a time. If you just go for gold (me), you can make an EASY 150k an hour, probably more. Bring a bag of sending or three lol.

To find the painted caves, follow the river that comes into the southwest corner of Trinsic. It heads southwest out of Trinisc. Follow it to it's source, the caves are on the north side of the river...if you are on the south side, there is a bridge across a couple screens east of the caves.